To celebrate, CNET has tracked down three rare and iconic Sony devices -- the original TPS-L2 Walkman, the sequel WM2 and the Sony Pressman, who's importance will become clear very shortly. Click through for a lesson in tech history, or hit the link below for the full-fat video version.

First up, meet the Sony TCM-100 voice recorder, also known as the Pressman. Ours is labelled the TCM-600, but don't worry -- that's just a name it was given in different markets. This humble gadget would form the basis of Sony's iconic Walkman device.

The Pressman was a full recorder packed with features, including sockets for an external microphone and headphones. Pay particular attention to the layout of these buttons, because they'll be important later.

Our TPS-L2 is an early model, because it doesn't have the Walkman branding on the side. It was originally called the Soundabout in the US, and in the UK it was the Stowaway, which makes it sound like it's going to hide in a grog barrel and eat all your ship's biscuits. Sony eventually settled on Walkman for every region, however.

Unfortunately there's one thing we weren't able to show here -- the original, miniature headphones that came bundled with the Walkman. Sony's Akio Morita says that developing these tiny 'phones was one of the most difficult parts of the Walkman project.

Despite an onslaught of rival devices, Sony remained the king of portable tunes. Ten years later Walkman sales hit 50 million; in 1992 they hit 100 million, with dozens and dozens of different models available, from toughened waterproof models and solar-powered players.